Conventional electronic devices typically had to address only a single heat source such as a microprocessor or processor module. While microprocessors or processor modules continue to increase in power consumption, the associated support circuitry is also increasing in power consumption. This increase is due to the need to keep up with the higher operating speeds and performance of the microprocessors. Additionally, support devices such as batteries are required to discharge and charge in limited temperature ranges in order to meet regulatory safety requirements. Ignoring the additional heating from these other sources can lead to catastrophic failures. Thus a need exists to simultaneously monitor multiple heat producing components.
Traditional temperature control devices monitored the temperature on a large thermal mass such as a heat sink attached to an integrated circuit (IC), such as a microprocessor or module, or even just the ambient air within a cavity of an electronic device. Due to the low thermal drop across the IC-heat sink interface, the heat sink monitoring was a sufficient indication of actual IC die temperature. With the advent of higher power devices such as Pentium III processors and 3D enabled graphic controllers, which operate at different power levels depending on the actual use, the drop across the IC-heat sink interface varies. A further concern is that due to higher levels of integration, more power is being expended in a smaller die or module area. Additionally, due to the need to support different optional configurations for a postponement manufacturing process, the thermal IC-heat sink interface may not be predictable. To ensure that the IC does not exceed its thermal design specifications, manufacturers of the ICs have begun to incorporate thermal diodes onto the IC die which allow external circuitry to monitor the forward voltage drop of the diode, thus providing an indication of die temperature. However, when the temperature is monitored on the die, there is little feedback on how the heat being dissipated from the heat sink or other heat dissipation structure is affecting other devices within the electronic device or the external surfaces of the electronic device. Therefore, a need exists to more accurately monitor individual die or module temperatures while also providing system wide thermal control.
Several different temperature sensors have been developed to measure the temperature of electronic devices and thermal surfaces. Traditionally, thermistors with either positive or negative thermal coefficients were used typically with bridge circuits to provide a difference signal that gave an indication of relative temperature change. As previously stated, the need to monitor die temperature directly has required that IC manufacturers develop diode temperature sensors which allow for easy fabrication using conventional IC processes. Since the forward voltage drop of the diode is non-linear with temperature, the diode temperature sensor is typically accompanied by a companion IC which provides an analog-to-digital conversion of the diode voltage drop and the accompanying non-linear to linear conversion. Thus, the output of the diode temperature sensor is a digital output and cannot be directly incorporated into conventional analog controller circuits. Therefore, a need exists to have a temperature control circuit which can support multiple types of temperature sensors.